


Nightmare does as he Pleases

by OnyxSinz (OnyxianDrake)



Series: Dark Love [6]
Category: Undertale (Video Game)
Genre: Against the Wall - Freeform, Alternate Universe - Crosstale | XTale (Undertale), Alternate Universe - Dreamtale (Undertale), Cervix Penetration, Dreamtale Nightmare Sans (Undertale), Exhibitionism, Humiliation, Killer Sans (Undertale) - Freeform, Multi, Past Rape/Non-con, Rape/Non-con Elements, Tentacles, Wall Sex, XTale Sans (Undertale) - Freeform, dub-con
Language: English
Status: Completed
Published: 2020-11-02
Updated: 2020-11-02
Packaged: 2021-03-08 23:15:05
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,245
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27354829
Author URL: https://archiveofourown.org/users/OnyxianDrake/pseuds/OnyxSinz
Summary: Cross thought he was free after the test, but Nightmare has other plans in mind.
Relationships: Krossmare - Relationship, Sans/Sans (Undertale)
Series: Dark Love [6]
Series URL: https://archiveofourown.org/series/1997761
Comments: 4
Kudos: 76





	Nightmare does as he Pleases

**Author's Note:**

> From Day 19 in my Kinktober 2020 piece.

“So the one time rule only applies to Killer then?” Cross mumbled, unable to put forward the stoicism he usually maintained or even some snark.

Nightmare’s tentacles were intruding under his clothes; teasing inside his ribcage, pushing down his shorts and curling around his pubic arch. All of it was sending warmth and magic to his cheeks and pelvis, only able to try and keep down the noises that threatened to escape him. It wasn’t as surprising as he thought it would be, but Cross still didn’t like the fact they were in the halls of the castle, instead of his own room or being taken to Nightmare’s.

“I never stated I’ve used Killer only once,” Nightmare purred, forcing Cross to look at him, a leering grin and half-lidded socket filling Cross’ sight. “In fact, I said you all belong to me, to do with as I wish. I believe it should be inferred that means  _ whatever _ I want.”

Cross shuddered, taking a shaky breath at the tentacle stirring the unformed magic slowly gathering in his pelvis. He couldn’t form it with the intrusion, but it was both a blessing and a curse, the contact with raw magic making his knees weak and threatening to make him lose control over his voice. He grabbed at Nightmare’s hoodie when the tentacle rubbed his arch as it pressed deeper, leaving him gasping before he clicked his mouth shut.

“I-in the hall?” Cross asked hesitantly, glancing around briefly.

“You didn’t seem terribly bothered by the audience last time.”

Cross flushed darker along his cheeks at the not completely untrue claim, unable to keep the whine from escaping when Nightmare slowly pulled the tentacle from his sensitive cloud of magic.

“Form your pussy for me.”

He locked up, fists tightening on the hoodie clenched in his hands as he hesitated, not meeting Nightmare’s gaze. Cross had only summoned it once after the incident he could only consider some kind of hazing ritual Nightmare did, where he’d been left sore, bloody and in a strange daze. There wasn’t much he could recall  _ after _ , a strange, warm fuzz and gentle hands before waking up in his bed, bones stiff and painful.

Even the week after he’d been cautious to summon  _ that _ again, alone or not, remembering the conflicting mix of pleasure and agony. Cross still couldn’t figure out if the confusion of the situation was muddling his feelings at the time, but he refused to believe he’d actually enjoyed the fact the pain had easily blurred together with his pleasure.

“I don’t-”

“Cross.”

Cross ducked his head obediently, magic filling out from his ribs to his knees, an uncomfortable wetness already slicking between his legs as Nightmare’s tentacle returned to nudge and rub along his slit.

“See,” Nightmare purred, tilting Cross’ face up to look at him in the socket. “You’re a proper slut for this kind of thing, Cross. I didn’t even expect you to be so wet already.”

Cross jolted, trying to defend himself as shame welled up in his soul. Instead, Nightmare’s teeth clacked against his, and his mouth was taken over by the other’s tongue, swallowing down his cry as the tentacle thrust into him. It was pain and bliss all at once, too much, and just enough to leave him caught between fighting and giving in. He arched when the tentacle rubbed hard and deep inside of him, applying too much pressure to his g-spot and the back of his magic.

All he could feel was pleasure as his orgasm hit suddenly, leaving him clawing at Nightmare’s shoulders, muffled by the kiss and feeling suffocated until he pulled away. Cross was left panting, trying to regain his bearings when he shivered harshly with a whine, feeling Nightmare’s tentacle nudging a deeper entrance he hadn’t realized he’d formed.

He gave up as the tentacle pulled out and Nightmare only moved closer, looming over him until he pulled Cross up by his thighs, shorts abandoned, and pressed him against the wall. Cross could feel the heat of Nightmare’s cock pressed between his folds, sliding easily with slow movements, leaving him stuck between moving with him or refusing to move.

“I-I’m not your slut,” Cross hissed weakly, turning his head away when Nightmare looked at him, refusing to acknowledge the power the other held over his head in the situation.

“...I think you’re whatever I want to call you,” Nightmare growled back. “But I do know you’re enjoying this...your negativity can only cover your pleasure to a point.”

Cross was cut off as he cried out when Nightmare thrust in, attempting to shove at his shoulders now before his hands were pinned over his head. It took all he had to keep from begging Nightmare to stop. Instead he gritted his teeth and held back moans and sobs, grunting when it felt like Nightmare might even force himself into whatever deeper expanse his magic had formed.

When one of Nightmare’s tentacles targeted his clit, Cross broke, pulling at where his hands were bound as another orgasm crashed through him.

“T-too much- please- Night-!”

Cross could barely see through his tears- he hadn’t even realized he was actually crying- but he caught a glimpse of someone behind the taller skeleton. His soul seized up in horror realizing Killer was leaned against the wall, watching with his wide grin. Once more he tried getting away, shame and embarrassment flooding his soul at being seen like this. He didn’t want to think of the fact Killer was probably enjoying the show, instead of helping him get away. It wasn’t like he  _ expected _ help from the psycho, even as desperate as he was for it.

A pathetic whine broke his begging as Nightmare painfully thrusted deep enough to get past whatever deeper part was trying to keep him out. An agonized moan followed soon after at the strange coldness that filled him, a weaker orgasm leaving him quivering with his forehead against Nightmare’s shoulder.

“Damn. I think ya broke him, boss,” Killer snickered, snapping Cross out of his blissed-out daze. “Got him crying and everything.”

Nightmare’s chuckle only added to Cross’ humiliation, but he managed to swallow down the sob that threatened to break what little control he was maintaining over his reactions. He jumped when Nightmare’s thumbs rubbed slow circles on his hips, not having realized he was being held there now.

“All the more reason to get him cleaned up and in his room.”

Nightmare purred as he pulled out finally, Cross painfully aware and sensitive to the feeling as he inhaled sharply. The sound of the purr confused Cross immensely, trying to remember any time Nightmare truly purred, unable to think of a single time.

“Hope ya didn’t fuck his brains out like last time. Need him coherent this time, remember?”

“I know very well what we discussed, brat.”

Killer snorted as Cross startled when Nightmare let his hands go and moved his legs off his hips. Off-balance and weak, he nearly collapsed before Nightmare had him in his arms, a very bewildering fact that had Cross trying to connect what the hell they were talking about.

“Doesn’t seem ya did a good job at it.”

“If he needs rest to come to his senses again then we’ll wait until then.”

“Whatever ya say boss.”

Needless to say, Cross still had no fucking idea what they were going on about as he slowly lost the fight with his exhaustion.


End file.
